Two hundred forty-five patients were studied prospectively to determine the value of endocervical curettage (ECC) in the follow-up of patients having undergone cryotherapy for cervical intraepithelial neoplasia (CIN). Patients at high risk of treatment failure were divided into three groups: (I) CIN grade 3 lesions confined strictly to the ectocervix (86 patients), (II) CIN grade 1-3 lesions involving the endocervix to a depth of up to 5 mm and a negative ECC prior to cryotherapy (64 patients), and (III) CIN grade 1-3 lesions confined to the ectocervix or extending into the endocervix to a depth of up to 5 mm and a positive ECC (27 patients). A fourth group, 68 patients with CIN grade 1 and 2 lesions confined to the ectocervix, was considered to be at low risk of treatment failure and served as controls. All the patients had satisfactory colposcopy. ECC was performed at 6 and 12 months after cryotherapy. Recurrent or persistent CIN was diagnosed in 19 of 245 patients (8%) and was found in group I (6 of 86, or 8%), II (6 of 64, or 9%), III (3 of 27, or 11%) and IV (4 of 68, or 6%). The rates of treatment failure did not differ significantly between the various groups (p greater than 0.1). ECC was positive in 4 of 19 (21%) of the cryotherapy failures (group I, 1 of 6; II, 2 of 6; III, 1 of 3; IV, 0 of 4). In two cases of a positive follow-up ECC, cervical cytology was also positive.(ABSTRACT TRUNCATED AT 250 WORDS)